audit: extend cartridge bundle to subsume backend FFI (#153)

Adds the 2 ffi/zig/src/{federation,cartridge_shim}.zig entries from PR #153
to this PR so a single audits/assail-classifications.a2ml lands without a
merge conflict between the two PRs.

Total entries: 119 (117 cartridge + 2 backend FFI).

Refs hyperpolymath/panic-attack#32. Supersedes #153.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath